Steering gear lubricant



Patented July 30, 194B UNETED STATES PATENT OFFICE STEERING GEAR LUBRICANT No Drawing. Application February 10, 1937, Serial No. 125,032

6 Claims.

The present invention relates to an improved lubricating grease and to the method for making same, more particularly to a solid grease capable of carrying heavy loads, showing little tendency to leak from housing, and at the same time having a low yield point even in the coldest weather. The present invention will be fully understood from the following description.

Lubricating greases consist largely of lubri- 10 cating oils in which various soaps are incorporated to produce what is known in the art as a grease structure. Various types of grease are made for difierent purposes ranging from the very soft to the very hard products. The soaps ordinarily employed are the soda and lime soaps, and in general the greases may be made harder by increasing the proportion of soap. However, it has been difficult to produce greases for certain purposes, in particular, for the lubrication of the steering gears of automobiles. Such a grease must be soft and must have the property of increasing in hardness to the least possible degree at low temperatures in order that steering effort shall not become too great in cold weather.

At the same time the grease should be solid under all temperatures of normal operation so as to prevent leaking from housing which is difficult to avoid with a liquid product. The known greases for this purpose are normally solids at operating temperatures but at low temperatures they-become so hard as to make steering dificult.

It has been found that an excellent grease of the above desired characteristics can be prepared by using a mixture of lime and aluminum soaps in place of the ordinal? soda and. lime soapsg The amount of each of these soaps may vary from about 1 to 7%, and it is preferred-that they should be in substantially equalproportions but the ainountof either one should not be'more 40 than about twice'the amount of the other. It is preferred that they should be present in the same amount. The actual-amount used will,'of course, depend to some extent on the service to which it is subjected, but the presence of the two soaps "in combination produces the desiredresult which cannot be accomplished by the presence of either alone. -In making up the present grease, it is preferred to use-aluminum stearate as the aluminum soap In producing the calcium soap any of preferred to use a good grade of low titre tallow. It is likewise preferred that there be a slight excess of the fatty acid over the alkali so as to obtain a grease of better quality.

The above ingredients are the essentials for the 5 present grease. It will be understood that other materials may be added, if desired, for example, extreme pressure agents may be added such as chlorine containing compounds either of the straight chain or ring types, or loosely bound sul- 10 fur compounds such as polysulfides,- sulfurized pine oil, or other'sulfurized terpenes or sulfurized fatty oils. These products may be made by subjecting a suitable organic compound of the types listed above to direct sulfurization with ele- 15 mentary sulfur, or may be treated with sulfur v chlorides. The presence of these materials'as stated above, is not essential to the present grease, but they give it additional ability to stand heavy loads, and are particularly desirable in 20 greases for automotive steering gears because such properties are especially desired in this service.

Inmanufacturing the'present grease, the preferred method is to separately prepare the alumi- 25 num and calcium soaps and then to incorporate each'of these soaps in a portion of the hydrocarbon oil by heating and agitating at an elevated temperature from 250 F. to 350 F. The

products are thencooled and a small amount of 30 water, say about 1%, is added to the oil containing the lime soap, in order to give it the grease structure. After these intermediate materials are cooledthey are then incorporated one with the'other and thoroughly blended, preferably at 35 low temperatures, or with gentle heating, if not too high, to remove the water and completely dehydrate the product.

The other materials may be added either before or after the grease has been formed, for example, 40

Example I A mixture containing 2.77 parts by weight of aluminum stearate and 65.54 parts of lubricating oil are heated to about 300 F. while agitated thoroughly to effect homogeneity. The product is then allowed to cool to room temperature. It is then found to be a thick, slightly cloudy oil without grease structure.

To about 83 parts of lubricating oil is then added about 12.5 parts of tallow and 1.4 parts of hydrated lime for saponification. This mixture is heated to about 350 F. to effect saponification and then allowed to cool to 200 F. when about 1% of water is added. Further cooling is then permitted and the compound develops the characteristic grease structure. The lime soap in the oil contains a slight excess of free fat or fatty acid over the alkali, and produces a softer product than would be the case if saponification were complete.

To parts of low cold test lard oil is mixed 5 parts of sulfur monochloride (S201 and the mixture is heated gently, while blowing with air to remove all HCl formed during the reaction, and without allowing the temperature to rise above about 140 F. The material is agitated until a small sample is removed and found not to darken a clean strip of copper. This should be accomplished in about 2 hours. The product is then cooled to room temperature.

The lime soap grease prepared above is then mixed with the suliurized lard oil in the proportion of about 17.77 parts of the former to 13.9 parts of the latter, and when this mixture is completed it is added to the dispersion of the aluminum stearate in oil in proportions so as to give about equal parts of aluminum stearate and calcium soap in the mixture. The final compound has the following composition:

Per cent Aluminum stearate 2.77 Calcium soap 2.77 Sulfurized lard oil 13.90 Mineral lubricating oil 80.36 Water 0.20

Total 100.00

This compound is found to have a well defined grease structure, is solid at ordinary temperatures encountered during driving and has a sufficiently high yield point so as not to readily flow or to leak from housing. At the same time it has a much lower yield point than ordinary soft cup greases at low temperatures. On reducing temperature it does not become excessively hard, as is the case with cup greases.

When tested on the Almen lubricating machine, the grease carried a load of 15,000 pounds with a very low frictional torque resistance. Tests were also made on the Gardner mobilometer at several temperatures and showed that the grease did not harden nearly so much when temperatures were reduced as is the case with cup or other ordinary greases. The grease serves as an excellent lubricant for automotive steering gears.

Example II A second grease was made up similar to that of Example I except with the following composition:

This was a solid at all or very high temperatures. It carries a load of 15,000 pounds on the Almen machine and 11,000 on the Almen shock load test.

Time per 10 centimeter pass of 51 hole disk. grams total load.

77 F. 20 F. 4 F.

Sample A 6. 3 48. 4 Sample B 6. 3

From this it will be seen that the improved grease containing both of the soaps did not become hard at low temperatures as was the case with Sample B, which contained only calcium soap.

The present composition, while it is especially useful for automotive steering gears is not limited to this particular use, as will be understood. The essential and distinguishing characteristic of this grease is the fact that it remains solid at ordinary temperatures of use, and does not become hard at temperatures below normal. It is thus a leak proof grease which retains a low yield point in cold Weather. The product may, therefore, be used wherever such a combination of properties is desired.

The present invention is not to be limited to any particular grease composition or method of manufacture nor to any specific amount of the aluminum or calcium soaps, but only to the following claims in which it is desired to claim all novelty inherent to the invention.

We claim:

1. A method of producing a lubricating grease composition, having a total soap content substantially within the range of about 2% to about 14%, comprising dispersing an aluminum soap in lubricating oil at an elevated temperature; dispersing a calcium soap in lubricating oil at an elevated temperature; cooling the dispersions, and adding a small amount, but less than 1%, of water to the dispersion containing calcium soap, producing a composition having a substantially stable grease structure; and at a temperature below that at which said grease structure is formed, incorporating the aluminumsoap-in-oil dispersion in a proportion to obtain a lubricating grease composition wherein the amount of one of said soaps does not exceed twice the amount of the other.

2. A lubricating grease composition, containing a total amount of substantially from 2 to 14% of aluminum and calcium soaps, and in which the amount of one of said soaps does not exceed twice the amount of the other, comprising an intimate mixture of a substantially water-free dispersion of an aluminum soap in a lubricating oil, with a calcium soap grease containing a lubricating oil, calcium soap and less than 1% of water, said mixture having the character of a substantially stable grease composition.

3. A lubricating grease composition according to claim 2, in which said aluminum and calcium soaps are obtained by saponification with a material selected from the group consisting of soap forming organic acids, glycerol esters of such to claim 2, in which the calcium soap contains a acids, and organic materials containing said slight excess of free fatty acid.

acids or esters. 6. A lubricating grease according to claim 2, in 4. A lubricating grease composition according which the aluminum and calcium soaps are in 5 to claim 2, in which-the calcium soap is obtained substantially equal proportions. 5

by saponification of hydrated lime with a low titre tallow in the presence of a lubricating oil. JOHN C. ZIMMER.

5. A lubricating grease composition according I ARNOLD J. MORWAY. 

